Date and time are represented in various notation formats. For example, date and time are represented by relative date and time notation that represents a specific date and time relative to a reference date and time, and by absolute date and time notation that represents a specific date and time in an absolute sense. Time is represented by the 24-hour time notation that represents a time of day in the 24-hour clock, and by the 12-hour time notation in which a day is divided into the morning and the afternoon and a time of day is represented in the 12-hour clock. In some cases, date and time are represented by using specific words for representing date and time, kanji (a Japanese writing system), and numerals.
In this condition, for example, when a user searches a text file for a specific date and time, search is performed by using date-time notation strings (date and/or time notation strings) in several different notation formats corresponding to the date and time that the user wants to find. For example, when the user searches for 15:00, search is performed by using “15:00”, and also “three o'clock in the afternoon” and “3:00 pm”.
Conventional technologies are known in which, when a user searches document data for a date-time notation string representing a specific date and time, and when a found date-time notation string is represented by relative date and time notation, a date-time notation string represented by absolute date and time notation is written, on the document data, next to the date-time notation string represented by relative date and time notation. Such a conventional technology is described in Japanese Laid-open Patent Publication No. 2003-050795, for example.
In document search, however, such a technology is expected not to make any change on the original document, and is also expected to present a text that has been found to the user, and thus, writing a date-time notation string represented by absolute date and time notation next to a date-time notation string represented by relative date and time notation is undesirable.